1. Background of the Invention
The present invention relates to a heat-driven pump, and particularly relates to a heat-driven pump which performs pumping by repeating generation and elimination of bubbles due to heat.
2. Prior Art
FIG. 20 illustrates a heat-driven pump disclosed in U.S. Pat. No. 4,792,283 issued to Applicant on Dec. 20, 1988. The disclosure of this patent is incorporated herein by reference.
In this heat-driven pump 51, a heating chamber 53 which is embedded in a heating portion 52 communicates to a vapor-liquid exchange chamber 54 through two passages: a condensation tube 55 and a liquid suction port 56. The vapor-liquid exchange chamber 54 communicates to both a suction tube 57 and a discharge tube 58. To allow liquid to flow only in a single direction, the suction tube 57 and the discharge tube 58 are connected to a suction side check valve 59 and a discharge side check valve 60, respectively.
The condensation tube 55 opens at an upper end thereof to the vapor-liquid chamber 54. A gap 61 is formed between the upper end of the condensation tube 55 and a lower end of the discharge tube 58 for allowing lquid to directly flow from the suction tube 57 to the discharge tube 58 through the vapor-liquid exchange chamber 54.
The liquid suction port 56 is partitioned into small opening areas by a plurality of radially extending fins 62.
The fins 62 are made of thin stainless plates, and are bonded through an adhesive or welded at regular angular intervals to the outer circumferential surface of the lower end of the condensation tube 55 as illustrated in FIG. 21.
In this heat-driven pump 51, the heating chamber 53 and the vapor-liquid chamber 54 are filled with liquid which is flowing from the suction tube 57. Bubbles are formed from the lower end of the heating chamber 53 by heating the heating portion 52. As a bubble grows, the interface between the bubble and liquid ascends, and then reaches to both the liquid suction port 56 and the lower end of the condensation tube 55. The interface is blocked at the liquid suction port 56 due to a capillary phenomenon caused by radial fins 62, and enters only the condensation tube 55.
During such a process, a volume of liquid which is equal to a volume of the bubble produced forcedly flows out of the heating chamber 53 into the vapor-liquid chamber 54, and is then delivered out through the discharge pipe 58.
The bubble which has entered into the condensation tube 55 is cooled by surrounding liquid, so that it contracts and then disappears. Thus, a volume of liquid which is equal to the volume of the bubble flows from the vapor-liquid exchange chamber 54 into the heating chamber 53 through the liquid suction port 56 and the condensation tube 55. Fresh liquid which is equal in volume to the liquid entered into the heating chamber 53 flows into the vapor-liquid exchange chamber 54 through the suction tube 57.
In this fashion, pumping of liquid is carried out by repeating production and elimination of bubbles caused by heat.
To fabricate the heat-driven pump 51, it is necessary to bond or weld each of radial fins 62 to the outer circumferential surface of the lower end of the condensation tube 55, and hence it is laborious to assemble the radial fins 62. Furthermore, radial fins 62 are liable to be separated from the condensation tube 55.